Gas flowmeters are valuable components of physical and biological systems that require measurement of gas flows for performance monitoring and process control. Gas flow measurement becomes challenging when flowrates are within the low-range regime (0.25 mL/min to 5,000 mL/min). In addition to flowrate, another challenge is the reactivity of gas-vapor components with contact elements in a flowmeter. Gas-vapor systems may be corrosive and non-corrosive.
The invention is a solution to the limitations of currently available gas flowmeter systems such as mass flowmeters, rotameters (variable area meters), and other IR-based bubble-through gas flowmeters, as applied to low-flowrate gas systems. A coriolis-type mass flowmeter relies on the vibrations of a tube system to measure the mass flowrate, which is then divided by the fluid density. Fluid density is significantly affected by temperature, pressure and gas composition. Rotameters measures flowrate by passing a gas stream into a variable cross-section area. A floating object is inserted in this flow tunnel to indicate flowrate level against a pre-calibrated graduation. Rotameters are not easily adaptable for electronic signal processing. Finally, a “bubble-through” type gas flowmeter works by passing the gas line through a liquid column; the bubble formation is correlated to gas volume. A bubble-through gas flowmeter utilizes a non-contact sensing mechanism. The detection unit, which is the gas bubble, passes through a detection region and vents out of the liquid column. Although a bubble-through design is the simplest setup that addresses the difficulty at low-flowrate regime, the bubble column of currently available bubble-through gas flowmeters is prone to significant back-flow volume due to pressure head. This effect results in a non-trivial alteration to the kinetics of gas flow.
Thus, there is a need for a bubble-through setup that can address the effects of back-flow volume through proper design of the region where gas enters and bubbles form. The sensing mechanism must also include a signaling setup that is not easily disturbed by extraneous effects such as changes in ambient light or vibrations/sound. A reliable signal system for this setup is an infrared beam, which is disturbed or “broken” only when a gas bubble passes through the infrared beam path. A gas flowmeter of this type may also be amenable to field applications, i.e., it may be portable to maximize its utility.
There are several potential applications for this invention. A sampling of those uses is presented below but is not meant to limit the invention. A person having ordinary skill in the art would understand that a flowmeter of this nature may have other uses as well. Such uses include biological applications such as (a) bench bioreactors and fermenters with gas production for application and laboratory reactors tracking gas generation for user; and (b) pilot bioreactors and fermenters with gas production for application and pilot-scale bioreactor operations for user. There are abiotic system uses such as (a) O2 and H2 generation for applications and batteries, and other electrolytic reactors for user; (b) CO2 evolution gas measurement for application and respirometers for user; (c) and gas measurement for mass balance tracking from reactors for application and laboratory scale abiotic reactors. It can be used in analytical apparatus for (a) measurement of physical properties of fluids, both gases and liquids; and (b) interaction of infrared with fluids. There are biomedical and related uses such as (a) O2 and air supply in life support systems for biomedical use; (b) general-purpose gas supply systems for biomedical use; (c) gas flow testing applications for calibration and maintenance of gas supply in life support systems and other biomedical devices for users; and (d) non-biomedical life-support systems that involve O2, air and other gases. Finally, the assembly can be used in educational platforms such as (a) experimental sensor in learning lab and class for schools; (b) experimental setup for the study of physical properties and behavior of fluids; and (c) training kit in itself and/or component of a training kit for building modular measurement systems in learning lab and class for schools.